Hi. Just want to know how to do a deed of sale if the new car was not yet fully paid but will be sold?

This is just an internal arrangement between two sisters. The 1st sister applied for the 2nd sister for easy approval from the bank. Then, the ownership of the new car will be transferred from 1st sister to 2nd sister thru deed of sale. What must be the content of the deed of sale in order to have it valid and honored. With regards to the payment of monthly installment no problem with that, it will be shouldered by the 2nd sister. The OR and CR of the car was not yet release as of this time. The new car is 3-weeks old only. Please help us. Thanks for your reply.